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Image Quality Considerations with Shared Photo Streams

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Q: It seems to me like the Shared Photo Stream feature is more targeted at people who share lots of photos of low importance. Sadly not for people who want to share treasured moments with close friends and family. I guess I still have to rely on e-mails for those full-sized photos?

A: Realistically, the Shared Photo Stream feature is primarily designed for sharing photos on iOS devices and viewing on the web, although it can also be synchronized to Aperture or iPhoto on a Mac or to a folder via the iCloud Control Panel on Windows.

The resolutions used in Shared Photo Streams compare quite favourably to most other social networks such as Facebook. More photo-focused services do provide full-resolution options, but many such as Flickr, require a paid “Pro” account to access this capability.

Unfortunately the race to continually drive up the number of megapixels in modern cameras has led many people to forget that most cameras already use resolutions that are significantly higher than strictly necessary for casual viewing and printing of photos.

A standard iPhone 5 photo in the Shared Photo Streams is stored at a resolution of 2048 x 1536. By comparison, a 1080p HDTV or typical computer display maxes out at around 1920 x 1080, and even the iPad Retina Display is only 2048 x 1536. This means that these photos are already at a resolution that is higher than almost any device that you would be using to actually view these photos; it would only be on a Retina Display MacBook Pro (2560 x 1600 / 2880 x 1800) where this might start to make a difference.

Similarly, 2048 x 1536 would suffice for printing photos at standard sizes up to and including 5” x 7”. Note that the math here for calculating printing requirements is relatively straightforward; simply multiply the inches by the desired DPI to get the number of pixels required, where 300dpi is considered to be the standard pixel density for a professional quality photograph. Therefore, a 5” x 7” print would ideally require a 1500 x 2100 source image; while 2048 is slightly lower on the long edge, the aspect ratio of the original photo and the 5” x 7” print don’t actually quite match up (1.33:1 vs 1.4:1), so a standard print wouldn’t fill the full 7” on the long edge anyway.

The bottom line is that the resolution used by Shared Photo Streams should be more than sufficient for the vast majority of users who are simply viewing photos on just about any device they could access them on, regardless of whether you’re sharing casual photos of low importance or treasured moments. Remember that the standard Photo Stream will still provide the full-resolution images to your own photo library for editing and archival; it’s only the Shared Photo Streams that store downscaled versions to save both storage space and bandwidth.

The only real exception is if those you are sharing with regularly need to edit your photos or make larger prints of them (e.g. 8” x 10”). In this case, it’s true that Shared Photo Streams will not be an ideal solution, but there are many alternatives out there that can provide more effective sharing of original, full-resolution photos even directly from your iOS device. For example, both Dropbox and Flickr provide native iOS applications that allow for original, full-resolution photo uploads, and Dropbox can even be configured to automatically upload all new photos from your Camera Roll, which can then be shared with other users—in their full resolution—via Dropbox shared folders or web links.

The tradeoff with third-party utilities such as this is that you lose the seamless iOS integration. Shared Photo Streams will update in the background and your friends and family don’t need to install an additional app on their devices and can receive automatic notifications whenever new photos are added. Third-party apps don’t get the same background privileges, requiring you to actually launch the app in order to upload photos—even if you’re using an automatic feature such as the one found in Dropbox—and to leave them running if you’re uploading more than a handful of images.

Of course, there is no reason you can’t use a hybrid of both solutions either. Shared Photo Streams can be a great way to highlight those photos that you want to share from your device right away, while a Dropbox folder can still be used for those friends and family who may want or need full-resolution versions of the photos for archival or editing.